The following acronyms are used in this disclosure:
CoMP Coordinated Multipoint
CP Cyclic Prefix
LTE Long Term Evolution (4G)
MAC Medium Access Control
NR New Radio (5G)
OFDM Orthogonal Frequency Division Multiplexing
PCI Physical Cell Identity
PHY Physical
PSS Primary Synchronization Signal
RRC Radio Resource Control
SB SS Block
SFN Single Frequency Network
SI System Information
SINR Signal to Interference plus Noise Ratio
SNR Signal to Noise Ratio
SS Synchronization Signal
SSS Secondary Synchronization Signal
TRP Transmission Reception Point
UE User Equipment
UMTS Universal Mobile Telecommunication System (3G)
In order to allow for flexible operation of wireless communication systems, such as LTE, UMTS and NR networks, for example, the network broadcasts system information (SI) to user equipment (UE). The SI may include information necessary for the UE to access the network, such as system bandwidth and random access configuration information, for example. The SI may be divided into different parts, for example into system information blocks as in LTE, or into minimal or other types of SI, as in NR. Furthermore, different SI parts may be delivered in different ways, for instance by broadcasting in one cell, single-frequency-network (SFN) transmission in multiple cells, multi-cast transmission to a set of UEs or unicast (dedicated) transmission to a single UE.
In a typical initial access procedure, a UE starts to search for synchronization signals (SS), where different SS typically correspond to different cells. Typically, different cells can be distinguished by different IDs, which are embedded in the SS. As discussed herein, terminology commonly used when describing an LTE system will be used, such as “Physical Cell Identity (PCI).” It should be understood, however, that the discussion of LTE systems is merely exemplary, and the present disclosure is not limited to LTE systems. In some systems, the SS is divided into multiple parts, where different parts carry an identity, and the PCI is a combination of the partial identities. In LTE, for example, the SS is divided into PSS and SSS, which both carry independent identities, and the PCI is a combination of the PSS identity and the SSS identity.
An SI validity area is a set of cells in which some or all SI is valid, as described in 3GPP TSG-RAN WG2 Meeting #95 (Aug. 22-26, 2016) document R2-165202 entitled, “Quantitative Analysis of On-demand SI Delivery,” the contents of which are incorporated herein it its entirety. By default and in state-of-the-art systems, the SI validity area is a single cell. However, by defining an SI validity area larger than one cell, a UE may avoid receiving and decoding the same (some or all) SI repeatedly when it moves between cells in the set. With a single-cell SI validity area, a UE needs to decode the SI each time it moves to a new cell, since it cannot assume that the SI of the new cell is the same as the SI of a previously received and decoded SI of another cell. Note that the SI validity area may be different for different parts of the SI as described in 3GPP TSG-RAN WG2 Meeting #95bis (Oct. 10-14, 2016) document R2-166353 entitled, “NR System Information Areas for Other SI,” the contents of which are incorporated herein it its entirety. For example, one SI part could be valid in a small number of cells, e.g. a single cell, and another SI part could be valid in a large number of cells. A group of cells for which a part of the SI is valid is also called a SI group herein.